The present invention relates to a hydraulic pressure control valve for use with a brake master cylinder.
A hydraulic pressure control valve of the kind referred to above is known from, for example, European Patent Application No. 0 157 158 A2 (corres. to Japanese Patent Application Laid-Open No. Sho 60-226347), GB Patent Application No. 2 195 408A or the like. The known control valve comprises a housing, and components parts arranged wtihin the housing such as a piston, a preload spring, a valve element and so on. The housing is divided into a pair of first and second members which are threadedly engaged with each other. The first member or a body member is formed with a connector portion for piping leading to a brake actuator such as a wheel cylinder for rear wheels. On the other hand, the second member or a closure member is formed with a mounting portion such as, for example, threads by which the hydraulic pressure control valve is mounted to a brake master cylinder.
However, the above-described conventional hydraulic pressure control valve has the following problem, because the housing is divided into the first and second members which are threadedly engaged with each other. That is, when the first and second members are connected together, the connection is accompanied with relative rotation between them. The relative rotation causes torsion to be applied to the preload spring which is one of the component parts within the housing. Alternatively or in addition, the relative rotation causes wear to occur on the piston, or causes the surface of the piston to be rubbed. These result in defects such as leakage of hydraulic fluid, defective movement or operation of some component parts, and the like.
Further, the conventional hydraulic pressure control valve has also the following problem. That is, when the component parts are assembled together to form the control valve, some of the component parts such as the piston and the like are incorporated in a space defined between the first and second members and, subsequently, the remaining component parts such as the valve element and the like are required to be inserted in the housing through an end of the second member remote from the first member. In other words, the component parts must be mounted to the second member through the opposite ends thereof. Thus, the assembling of the control valve is troublesome and cumbersome, and it takes a considerable time for the assembling, resulting in an increase in the assembling cost, which, in turn, results in an increase in the manufacturing cost of the control valve.